Henley on byelection alert after Johnson takes Commons bow

Boris Johnson resigned as a Conservative MP yesterday with a final flourish in the House of Commons, paving the way for a byelection in his Henley constituency which the Tories hope will set the seal on a series of recent electoral victories.

A writ will be moved in the Commons today after Johnson triggered an arcane process to stand down as an MP, allowing a byelection to take place in Henley on Thursday June 26.

The Tories, who held the seat with a 12,793 majority at the 2005 general election, hope to secure a strong result on the eve of Gordon Brown's first anniversary as prime minister on June 27.

"We are not taking anything for granted," one senior Tory source said. "David Cameron has been clear that there is no such thing as a safe seat when it comes to byelections."

The Henley byelection will formally be announced today after Johnson took his leave of the Commons after seven years as an MP with a typically idiosyncratic intervention at prime minister's questions. He thanked the Speaker, Michael Martin, for his kindness before asking Gordon Brown to endorse his first announcements as London mayor.

To cheers from Tory MPs, Johnson asked: "Can I use my last few seconds in this great cockpit of our nation to ask the prime minister to join me in congratulating the London authorities on successfully implementing the ban on alcohol on tubes and buses, and on doubling the safer transport teams so that we will have more uniformed people on buses than at any time in the last 25 years?"

As he tried to continue, the Speaker interrupted the "lord mayor" to say he was "boss in here" and said he had asked enough questions. The prime minister said he welcomed the ban on alcohol as he pointedly praised Johnson. "I am sure that the whole house is going to miss the contributions of [Johnson], not only in speech, but in writing. Those have been more significant over the last few years."

Shortly afterwards Johnson ended his Westminster career by applying for an office for profit under the crown, because MPs cannot simply resign. He applied to be steward of the manor of Northstead.

Johnson announced his intentions a few hours earlier at his first press conference as London mayor. "It will be a huge wrench for me to leave Henley, which is of course full of the nicest, kindest and most wonderful people in the world outside London, but I do so, of course, because this job here in City Hall is simply too big and it is growing all the time," he said.

The Tories have laid careful plans for the Henley byelection to ensure they do not fall victim to "yellow peril", their term for the threat posed by the Liberal Democrats, who came second in the constituency in 2005. Henley is the sort of affluent southern seat where the Lib Dems scored strong byelection victories in the mid-1990s.

But Cameron made two decisions after Johnson's victory in the London mayoral contest to meet any Lib Dem challenge. He decided to hold an early byelection, to stop the Lib Dems building momentum, and he told the Henley Conservative association that they had to select a local candidate. This meant gently telling the association they could no longer have a high-profile MP - Johnson was preceded by Michael Heseltine - and informing the mayor's father, Stanley Johnson, that he could not succeed his son as MP for Henley.

John Howell, a Henley resident for 20 years who is an Oxfordshire county councillor, was duly selected as the Tory candidate last week. The Lib Dems deselected their candidate and chose Stephen Kearney, who lived in Plymouth until a few weeks ago.

The Lib Dems know that Henley is an important test for them: Chris Rennard, their byelection supremo, has been despatched to Henley. The Lib Dems know they are unlikely to pull off a byelection upset in Oxfordshire while the Tories are so far ahead in the polls. But they hope to show they still present a threat.

Labour, which won only 14.8% of the vote in the constituency in 2005, will be hoping it does not lose its deposit. That will happen if candidate Richard McKenzie fails to secure 5% of the vote.

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